Multirouter APS on the Cisco 10000 Series

This feature provides multirouter automatic protection switching (multirouter APS) on the Cisco 10000 series routers. APS refers to the mechanism of using a protect interface in the SONET network as the backup for a working interface. When the working interface fails, the protect interface quickly assumes its traffic load. In a multirouter environment, this feature allows the protect SONET interface to reside in a different router from the working SONET interface. This feature supports High Availability.

Release

Modification

12.0(23)SX

This feature was introduced on the OC3ATM and OC12ATM line cards for the Cisco 10000 series.

12.0(26)S

This feature was integrated into Cisco IOS Release 12.0(26)S, and support was added for the CHOC12, CHSTM1, OC3POS, and OC12POS line cards for the Cisco 10000 series.

Feature History for the Multirouter APS on the Cisco 10000 Series Feature

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Information About Multirouter APS on the Cisco 10000 Series

Multirouter APS

Multirouter APS provides the ability to switch SONET connections between two different routers in the event of a circuit failure. The ability to switch from one SONET circuit to another SONET circuit in the event of circuit failure is often required when SONET equipment is connected to telco equipment. SONET interfaces can be switched in response to a router failure, degradation or loss of channel signal, or manual intervention.

The protection mechanism used for this feature has a linear 1+1 architecture as described in the Bellcore publication TR-TSY-000253, SONET Transport Systems; Common Generic Criteria, Section 5.3. The connection may be bidirectional or unidirectional and revertive or nonrevertive.

In the 1+1 architecture, a protect interface (circuit) is paired with each working interface. Normally, the protect and working interfaces are connected to a SONET ADM (add/drop multiplexer), which sends the same signal payload to the working and protect interfaces. Figure 1 shows a multirouter APS configuration with Packet-over-SONET (POS) interfaces with the working and protect circuits terminating in different adapter cards in two different routers. Multirouter APS also supports ATM and channelized SONET interfaces. Interfaces in a multirouter APS configuration can be configured with either SONET or SDH framing.

Figure 1 Multirouter APS Configuration

On the protect circuit, the K1 and K2 bytes from the line overhead (LOH) of the SONET frame indicate the current status of the APS connection and convey any requests for action. This signalling channel is used by the two ends of the connection to maintain synchronization.

The working and protect circuits themselves, within the router or routers in which they terminate, are synchronized over an independent communication channel, not involving the working and protect circuits. This independent channel may be a different SONET connection or a lower-bandwidth connection. In a router configured for multirouter APS, the configuration for the protect interface includes the IP address of the router (normally its loopback address) that has the working interface.

High Availability APS on the Cisco 10000 Series

To support high availability (HA), APS state information is maintained on the secondary performance routing engine (PRE). The primary PRE synchronizes incoming events that affect the APS state with the secondary PRE as the events occur. When a new secondary PRE starts, HA APS synchronizes the current APS state to the newly started secondary PRE to initialize the APS state.

What to Do Next

Configuring Multirouter APS with Static Routes

Perform this task to configure the optional ip route static update immediate command for APS configurations on a Cisco 10000 series router with a limited number of static routes. To improve the router performance when only a few routes are configured, use static routes instead of dynamic routing protocols. The static route must be configured to ensure that traffic will still flow after a switch to the secondary processor. We recommend specifying the optional static route IP address of the interface to improve the routing performance.

Specifies the interface type and number and enters interface configuration mode.

Step 8

ip route static update immediate

Example:

Router(config-if)# ip route static update immediate

(Optional) Specifies that static routes will be added to the routing table immediately after the interface becomes active.

Step 9

carrier-delay [seconds | msec seconds]

Example:

Router(config-if)# carrier-delay msec 8

Sets the carrier delay timer value in seconds or milliseconds.

•This command allows link outages to be filtered and not reported as a link down event if they occur before the carrier delay timer expires. In multirouter APS system performance can be enhanced if link down event messages are kept to a minimum.

Step 10

aps group group-number

Example:

Router(config-if)# aps group 1

Permits more than one APS protect and working interface to be supported on a router.

Configuration Examples for Multirouter APS on the Cisco 10000 Series

Multirouter APS: Example

Using the configuration shown in Figure 1, the following example shows the configuration of multirouter APS. Router A is configured with the working interface, and Router B is configured with the protect interface. If the working interface on Router A becomes unavailable, the connection will automatically switch over to the protect interface on Router B.

On Router A, which contains the working interface, use the following configuration:

configure terminal

interface pos 1/0/0

ip address 10.7.7.7 255.255.255.0

!

redundancy

associate slot 3 mr-aps

!

interface pos 2/0/0

aps group 1

aps working 1

On Router B, which contains the protect interface, use the following configuration:

configure terminal

interface pos 1/0/0

ip address 10.7.7.6 255.255.255.0

!

redundancy

associate slot 2 mr-aps

!

interface pos 3/0/0

aps group 1

aps protect 1 10.7.7.7

Two Multirouter APS Groups: Example

The following example shows the configuration of two multirouter APS groups.

On Router A, which contains both a working interface and a protect interface, use the following configuration:

configure terminal

interface pos 1/0/0

ip address 10.7.7.7 255.255.255.0

!

redundancy

associate slot 2 mr-aps

associate slot 3 mr-aps

!

interface pos 2/0/0

aps group 1

aps working 1

!

interface atm 3/0/0

aps group 2

aps protect 1 10.7.7.6

On Router B, which contains the protect interface and a working interface, use the following configuration:

configure terminal

interface pos 1/0/0

ip address 10.7.7.6 255.255.255.0

!

redundancy

associate slot 3 mr-aps

associate slot 2 mr-aps

!

interface pos 3/0/0

aps group 1

aps protect 1 10.7.7.7

!

interface atm 2/0/0

aps group 2

aps working 1

Multirouter APS with Static Routes: Example

Using the configuration shown in Figure 1, the following example shows the configuration of multirouter APS with static routes. Router A is configured with the working interface, and Router B is configured with the protect interface. If the working interface on Router A becomes unavailable, the connection will automatically switch over to the protect interface on Router B. Note that 172.17.1.0 is the address of the traffic destination network and that the route over the Peer Group Protocol (PGP) link has a higher distance metric number than the multirouter APS working interface.

On Router A, which contains the working interface, use the following configuration:

configure terminal

interface pos 1/0/0

ip address 10.7.7.7 255.255.255.0

ip route static update immediate

carrier-delay msec 8

!

redundancy

associate slot 2 mr-aps

!

interface pos 2/0/0

aps group 1

aps working 1

ip route static update immediate

carrier-delay msec 8

!

ip route 172.17.1.0 255.255.255.0 pos 2/0/0 10

ip route 172.17.1.0 255.255.255.0 pos 1/0/0 10.7.7.6 20

On Router B, which contains the protect interface, use the following configuration:

RFCs

RFCs

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

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associate slot

To logically associate slots for automatic protection switching (APS) processor redundancy, use the associate slot command in redundancy configuration mode. To disable slot associations, use the no form of this command.

Single Router APS

associate slot slot-one slot-two

no associate slot slot-one slot-two

Multirouter APS

associate slot slot-one mr-aps

no associate slot slot-one mr-aps

Syntax Description

slot-one

First slot number to be associated for redundancy. Valid range is from 0 to 8.

slot-two

Second slot number to be associated for redundancy. Valid range is from 0 to 8.

mr-aps

Specifies that the slot association is between slots in different routers as part of a multirouter APS configuration.

Defaults

No slots are associated.

Command Modes

Redundancy configuration

Command History

Release

Modification

12.1(5a)EY

This command was introduced.

12.0(23)SX

The mr-aps keyword was added to support multirouter APS on the OC3ATM and OC12ATM line cards for the Cisco 10000 series.

12.0(26)S

This command was integrated into Cisco IOS Release 12.0(26)S, and support was added for the CHOC12, CHSTM1, OC32POS, and OC12POS line cards for the Cisco 10000 series.

Usage Guidelines

Use the associate slot command for single router APS or multirouter APS configurations on a Cisco 10000 series router. This command is specific to the Cisco 10000 series. The associated slots must use the same type of interface module and must be adjacent slots, for example slots 5 and 6.

Use the mr-aps keyword in a multirouter APS configuration to allow a protect interface on a second router to be a backup for a working interface on the first router.

Examples

The following example shows how to associate two slots in the same router in a single router APS configuration:

Router1(config)# redundancy

Router1(config-r)# associate slot 3 4

The following example shows how to associate two separate slots in different routers in a multirouter APS configuration:

Router1(config)# redundancy

Router1(config-r)# associate slot 3 mr-aps

!

Router2(config)# redundancy

Router2(config-r)# associate slot 2 mr-aps

Related Commands

Command

Description

redundancy

Enters redundancy configuration mode.

ip route static update immediate

To add static routes to the routing table immediately after an interface becomes active, use the ip route static update immediate command in interface configuration mode. To restore the default condition of waiting for a route dampening delay interval before adding the static route, use the no form of this command.

ip route static update immediate

no ip route static update immediate

Syntax Description

This command has no arguments or keywords.

Defaults

Static routes are added after a route dampening delay interval.

Command Modes

Interface configuration

Command History

Release

Modification

12.0(26)S

This command was introduced on the Cisco 10000 series.

Usage Guidelines

Use the ip route static update immediate command in a multirouter automatic protection switching (APS) configuration if there are a limited number of static routes. The command can be used on Gigabit Ethernet, ATM, channelized, and Packet-over-SONET (POS) interfaces that have static routes configured. This command is specific to the Cisco 10000 series.

Examples

The following example shows how to configure static routes to be added to the routing table immediately after an interface becomes active: